ORDER CARNIVORA. 



I427 



in a fossil state. The species of Lutra are characterised by the 

 great constriction of the skull in the orbital region, and usually by 

 the more or less squared contour of the crown of the upper true 

 molar, and the great development of the inner tubercle of the last 

 upper premolar, which forms a crescentoid ridge ; both these features 

 being well shown in fig. 1303. In the typical Z. vulgaris the dental 



formula is I. -, C. 



P?n. -, M. -, but in some existing species the 

 3 2 



3 1 



first upper premolar may be absent (fig. 1303), and other variations 

 occur in fossil forms. This genus may be divided into three groups, 

 which it is quite permissible to regard as distinct genera, and of 

 which the first and third are extinct. The Enhydriodont, or most 

 specialised group, comprises two large otters respectively from the 

 Pliocene Siwaliks of India and the Middle Miocene of Italy, which 

 attained dimensions fully equal to those of the existing Z. brasiliensis. 

 In both these forms the first upper premolar is absent, and in the 

 Indian Z. sivalensis the second premolar may likewise disappear. 

 In this species, moreover, the fourth upper premolar or carnassial 

 (fig. 1305) differs from 

 that of all other otters 

 in that the inner crescent 

 consists of three distinct 

 tubercles ; but the Italian 

 Z. Cainpanii (fig. 1304) 

 connects in this respect 

 the Indian species with 

 the true otters. The 

 typical group, which in- 

 cludes all the existing 

 forms, is known to date from the Middle Miocene of Europe, and 

 also occurs in the Tertiaries of America and the Indian Siwaliks. 

 Remains of the existing L. vulgaris occur in the Norfolk Forest- 

 bed ; while the Siwalik Z. palmndica is closely allied in the structure 

 of its teeth and skull to the living hairy-nosed otter (Z. sumatrana) 

 of Asia. Finally, the Lutrictine group is represented only by Z. 

 Valetoni, of the Lower Miocene of the Continent, which is dis- 

 tinguished from all other Mustelines by the presence of a minute 

 second upper true molar. This species is also characterised by the 

 narrowness of the first upper true molar, and by the circumstance 

 that the anterior upper premolars are placed immediately behind 

 the canine, instead of being squeezed towards its inner side, as in 

 fig. 1303. If regarded as generically distinct, this form should be 

 known as Potamotherium. The Miocene Trochictis appears to 

 connect the Otters with the Weasels. 



Among the Badgers and their allies extinct species of the type 



Fig 1304. — The right 

 upper carnassial of Lutra 

 Campanii; from the Mio- 

 cene of Italy. In its na- 

 tural position the outer 

 ridge would be oblique, 

 as in fig. 1303. 



Fig. 1305. — The left upper 

 carnassial of Lutra sivalen- 

 sis ; from the Pliocene of 

 India. The outer ridge is 

 broken. 



